Currently, ADS (Advanced Super Dimension Switch) is a hard-screen display panel, and the following defects easily occur during a rubbing process.
1 Peripheral block. The state of a rubbing cloth is affected by the dummy region between display panels. When the substrate (e.g., a glass substrate) is offset on a rubbing machine by an angle as small as 0.1°, this defect occurs.
2 Electrical test pad V-Block. Since the state of the rubbing cloth is affected bin a region where an electrical test pad is arranged, V-Blocks occur in corresponding regions.
3 Bonding pad V-Block. The state of the rubbing cloth is affected by the state of wirings in the bonding pad region, and V-Blocks of a wide strip shape occur at the middle of the display panel.
4 Cell pollution/Drop Mura. The rubbing effect in the SD Shadow (data line shadow) region is poor, and leakage defect occurs.
5 Rubbing Mura. Other factors cause inhomogeneous rubbing, and vertical Mura occurs.
The basic cause for these rubbing related defects lies in that morphological difference in the substrate affects the state of the rubbing cloth, and thus leads to alignment difference.
Rubbing Mura is a serious quality problem arising from the fabrication process, severely affects the picture quality, and has a low detection rate in the electrical test. This not only leads to great waste in materials and equipment at the back end, but also leads to a quality problem. Especially for a high-end product like ADS, improving Rubbing Mura is of vital importance, because with increasing requirement of the customer experience, the requirement for Rubbing Mura is increasingly strict. The basic cause for this defect is not the rubbing process, and the improvement by optimizing the process is limited.